I’ve been testing out working with Posca Markers, which are opaque liquid ink markers. Advertised as “mark vividly on any surface” I’ve found that the type of paper used really makes a difference in how they lay down (or tear up the paper), and that some colors seem more opaque than others. Testing out a new tool or material always takes some getting used to, especially if you have an idea of how it’s supposed to work versus how it actually works. So far the best success I’ve had with Posca Markers are for simple pieces.